Cooling of flame proof motors



July 4, 1961 J. K. VOSE ETAL 2,991,377 COOLING OF FLAME PROOF MOTORSFiled Jan. 22, 1958 5 Sheets-Sheet 1 July 4, 1961 J. K. VOSE ETAL2,991,377

COOLING OF FLAME PROOF MOTORS Filed Jan. 22, 1958 5 Sheets-Sheet 2 fwM y1961 J. K. VOSE ET AL 2,991,377

COOLING 0F FLAME PROOF MOTORS Filed Jan. 22, 1958 5 Sheets-Sheet 3 July4, 1961 J. K. VOSE ET AL COOLING OF FLAME PROOF MOTORS 5 Sheets-Sheet 5Filed Jan. 22 1958 wwe M J; E w W #0 wmwm United States Patent Q2,991,377 COOLING OF FLAME PROOF MOTORS John Kenneth Vose, Sale, andGeorge Willoner, Stretford, England, assignors to Metropolitan-VickersElectrical Company Limited, London, England, a British company FiledJan. 22, 1958, Ser. No. 710,506 Claims priority, application GreatBritain Jan. 28, 1957 3 Claims. (Cl. 310-61) The present inventionrelates to totally enclosed flame proof motors or explosion proof motorsand is concerned with the cooling of such motors.

When two chambers are connected by passages of small cross-sectionalarea, if an explosion occurs in one chamber the flame resulting fromthat explosion will travel through the connecting passage to the otherchamher where it will cause burning with detonation of gases alreadycompressed by the pressure wave preceding the flame.

It is known to cool motors by passing the cooling fluid through ductscut axially in the rotor but if this method is used in flame proofmotors the conditions for easy ignition of the gas masses at each end ofthe rotor as described above are obtained.

The object of the present invention is to cool the rotors of flame proofmachines without introducing conditions which will cause easy ignitionof combustible gases which exist in the motor and thereby damage to themachine.

According to the present invention the rotor of a totally enclosedflame-proof machine has a cooling system comprising a plurality of ductsextending longitudinally in the core of the rotor, each duct having anexit and an entry aperture at the same end of the rotor, means forpassing a primary cooling fluid through the cooling ducts and means forcooling said primary cooling fluid after it has emerged from the ducts.

In a particular embodiment of the invention the cooling system comprisesa heat exchanger associated with each end of the rotor, means forpassing the primary coling fluid after it has emerged from the ductsthrough the heat exchanger associated with that end of the rotor fromwhich the fluid has emerged and a supply of a secondary cooling fluidfor removing heat from said heat exchangers.

The present invention utilises cooling ducts in the rotor of a machinebut since these ducts have entry and exit apertures at the same end ofthe rotor there is no narrow neck connecting the two ends of the rotorthereby allowing the passage of a pressure wave and a flame from one endof the motor to the other. This avoids the dangerous conditions asdetailed above because the air gap between the stator and the rotor istoo small to allow passage of a pressure wave and a flame. The coolingsystem according to the invention is therefore suitable for use wheregases of group III (that is ethylene and the like) may be present in thecoolant fluid.

The invention will now be described with reference to the drawingsaccompanying this specification in which:

FIG. 1 is a longitudinal section of a portion of a rotor of a flameproof machine with cooling ducts therein and a fan and heat exchangerfor the cooling fluid;

FIG. 2 is a cross-section of the portion of the rotor taken on the lineI1III of FIG. 1;

FIG. 3 is a cross-section of a portion of the heat exchanger in FIG. 1along IIIIII;

FIG. 4 shows an alternative form of cooling ducts in a rotor;

FIG. 5 is a cross-section of the rotor in FIG. 4 along V-V;

FIG. 6 shows another alternative form of cooling ducts in a rotor of aflame proof machine;

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FIG. 7 is a cross-section of the rotor in FIG. 6 along VIIVII;

FIG. 8 shows another alternative form of cooling ducts in a rotor of aflame proof machine;

FIG. 9 is another cross-section of the rotor in FIG. 8 along IXIX;

FIG. 10 is another alternative form of cooling ducts in a rotor of aflame proof machine;

FIG. 11 is a cross-section of the rotor in FIG. 10 along XI-XI, and FIG.12 is a cross-sectional view of one of the heat exchangers with meansfor circulating the secondary cooling fluid therethrough.

With reference to FIGS. 1 and 2, a flame proof motor has frame 1 andstator windings and laminations 2 and rotor end windings and laminations3. The central windings and laminations of the rotor are represented by13. The shaft 4 of the rotor has a fan 5 mounted on it. 6 and 6' are thefins of a heat exchanger attached to the circumference of the frame 1extending radially inwards and outwards. 7 is a cylindrical baffleattached to 8 which is an annular batfie supported from the end of theframe 1 by arms 9. A cylindrical baflle 10 is attached to the end of therotor. 14 is a ring attached to the shaft 4 and welded to said ring area plurality of arms 15 extending axially along the shaft as far as thelaminations 13, and radially as far as and supporting the laminations 3.The laminations 13 are in the centre of the rotor and have no aperturestherein. The flat bars 12 are welded between successive arms 15 and formducts 11 and 18 which extend axially as far as the laminations 13. Thestator end windings are represented by 16. A series of holes 19 areformed in the disc of the fan 5.

With reference to FIG. 3 the fins 6 and 6' of the heat exchanger extendradially inwards and outward from the frame 1 of the stator. 17 is acylindrical plate situated encircling the stator frame and adjacent tothe outer fins 6' and cooling fluid is passed between 6' and 17 toremove the heat from the fins. The cylindrical baflle 7 is situatedadjacent to the ends of the fins 6.

The operation of the cooling system is as follows. The fan 5 rotateswith the shaft and causes circulation of cooling fluid along paths asindicated by the arrows. Two alternative paths are shown, the firstthrough each of the cooling ducts 18 and 11 in the rotor and out throughthe holes 19 and back to the blades of the fan and the second over thestator end windings 16 along the fins 6 of the heat exchanger where heatis given up to the fins and deflected by the baflle 8 back to the bladesof the fan.

The cooling fluid absorbs heat from the rotor in the ducts 18 and 11 andfrom the stator end windings and gives it up to the heat exchanger bypassing along fins 6. The second cooling fluid on passing between 17 andthe outer fins 6 removes heat from the latter.

The figure shows only one end of the rotor and it is assumed that theother end of the rotor is cooled by a similar method, the cooling ductsextending as far as the rotor laminations 13.

There has been described above a method of cooling the rotor of atotally enclosed flame proof machine by forming ducts within the rotorand passing cooling fluid through the ducts and removing heat from thecooling fluid by a heat exchanger which forms part of the frame of themotor without introducing dangerous conditions leading to detonation oflarge masses of gas at high pressure, thereby endangering the integrityof the flame proof enclosure.

FIGS 411 illustrate four alternative ways of forming the cooling ductsin the rotors of such machines. Corresponding items have been given thesame numbers in each figure. It is assumed that a heat exchanger similarto that shown in FIGS. 1, 2 and 3 will be incorporated in each of thesecooling circuits.

With reference to FIGS. 4 and 5 the ducts 18 have been increased in sizeand extend further radially into the laminations 3 as shown. 7

The paths for the cooling fluid are the same as in FIG. 1. Increasedcooling is obtained as a greater area of pressings is exposed to thecooling fluid but a certain amount of rigidity of the rotor is lost. 7

With reference to FIGS. 6 and 7 the ducts in the rotor are and 21. 20consists of a series of cylindrical axial ducts in the laminations 3,and 21 consists of a series of larger ducts extending axially adjacentto the rotor. These two sets of ducts are joined by suitable slots 26 inlannnations 22, which pressings are situated between 3 and 13. Thecooling fluid flows through 20 and 21 and then back through holes 19 inthe fan disc.

With reference to FIGS. 8 and 9 the ducts are 24 and 25 joined by slots26 in laminations 23. Ducts 24 conslst of a series of cylindrical axialducts arranged radially in pairs and ducts 25 consist of another seriesof cylindrical axial ducts also arranged radially in pairs on a smallerradius than 24.

These ducts extend axially through the laminations 3 and are joined byslots 26 formed in laminations 23 which are situated between 3 and 13.

The cooling fluid flows in through ducts 24 through slots 26 and outthrough ducts 25 and through holes 19 in the fan disc as before.

With reference to FIGS. 10 and 11 these show a section of a completerotor. Ducts extend along the whole length of the rotor and comprise aseries of pairs of ducts 30, 3 1, and 32, 33. The two sets of ducts arequite independent, and extend respectively from either end of the motor.Considering the right hand end of the motor, with reference to FIG. 10,the end plates 36 and 37 have pairs of holes therein corresponding withthe ducts 32 and 33, and the end plate 34 has a series of slots 39connecting pairs of ducts 32 and 33. The cooling fluid flows from fan 5into the rotor through ducts 32, through slots 39, out through ducts 33,and through holes 19 back to the fan. Considering the left hand end ofthe rotor, end plates 34 and 35 have pairs of holes thereincorresponding with the ducts 3t) and 31, and the end plate 36 has slots38 connecting pairs of ducts and 31. The cooling fluid flows from fan28, is deflected from cylindrical baflle 27 into ducts 31), throughslots 38, out through ducts 31, and through holes 29 back to the fan.

By an arrangement as detailed in FIGS. 10 and 11 cooling ducts areintroduced throughout the length of the rotor without producing thedangerous conditions as described above.

FIG. 12 shows a particular method of circulating the secondary coolingfluid, through one of the heat exchangers. The fins 6' are surrounded bya cylindrical plate 17 and the ends of this plate are closed by twoannular plates 41 and 42. These two annular plates have apertures 43 and44 and to these apertures are respectively attached two pipes 45 and 46as shown. At their remote ends these pipes are connected to a fan orpump 47. Operation of fan 47 causes secondary cooling fluid to becirculated through the pipes 45 and 46 into the annular chamber formedby plates 17, 41 and 42 and the outside of the stator frame 1, and overthe fins 6'. The secondary cooling fluid will in its turn be cooled bypassage through the pipes which are exposed on their out sides to thesurrounding atmosphere. 7

Even though a particular type of heat exchanger has been described itwill be appreciated that it is possible to use any of the arrangementsof rotor cooling ducts as described above with another suitable heatexchanger.

What we claim is:

1. A totally enclosed flame proof machine comprising a rotor having acore and disposed within an enclosing casing defining a chamber, meansproviding surfaces defining a plurality of ducts extendinglongitudinally within the core of the rotor of said machine andterminating at their inner ends within said core, and means forconnecting together the inner ends of said ducts in groups so as to forma plurality of discrete U-shaped passages of substantially constantcross sectional area for the passage of a cooling fluid, said surfacesterminating at their outer ends at the ends of the rotor core anddefining therein a plurality of entry and exit apertures for saidpassages connecting directly with the chamber defined by said casing,the arrangement being such that each passage has an entry aperture andan exit aperture at the same end of the rotor.

2. A totally enclosed flame proof machine comprising a rotor having acore and disposed within an enclosing casing defining a chamber, meansproviding surfaces defining a plurality of ducts extendinglongitudinally from either end within the core of the rotor of saidmachine and terminating at their inner ends within said core, and meansfor connecting together the inner ends of said ducts in groups so as toform a plurality of discrete U-shaped passages of substantially constantcross sectional area extending from each end of said rotor core for thepassage of a cooling fluid, said surfaces terminating at their outerends at the ends of the rotor core and defining therein a plurality ofentry and exit apertures for said passages connecting directly with thechamber defined by said casing, the arrangement being such that eachpassage has an entry aperture and an exit aperture at the same end ofthe rotor.

3. A totally enclosed flame proof machine. comprising a rotor having acore and disposed within an enclosing casing defining a chamber, meansproviding surfaces defining a plurality of ducts extendinglongitudinally from either end within the core of the rotor of saidmachine, extending substantially over the whole length of the core andterminating at their inner ends within said core, and means forconnecting together the inner ends of said ducts in groups so as to forma plurality of discrete U-shaped passages of substantially constantcross sectional area extending from each end of said rotor coresubstantially over the whole length of the core for the passage of acooling fluid, said surfaces terminating at their outer ends at the endsof the rotor core and defining therein a plurality of entry and exitapertures for said passages connecting directly with the chamber definedby said casing, the arrangement being such that each passage has anentry aperture and an exit aperture at the same end of the rotor.

References Cited in the file of this patent UNITED STATES PATENTS1,700,840 Gay Feb. 5, 1929 2,159,087 Ieflrey May 23, 1939 2,214,592Mueller Sept. 10, 1940 2,692,956 Kaczor et al. Oct. 26, 1954 FOREIGNPATENTS 16,590 Great Britain of 1914 337,334 Great Britain Oct. 30, 1930

